The tweet from Trump came hours after a terrorist attack in Barcelona that has lead to at least 13 deaths. Trump initially responded to the van attack in a measured tweet that told Barcelona to “be tough & strong.”

Later, however, he tweeted, “Study what General Pershing of the United States did to terrorists when caught. There was no more Radical Islamic Terror for 35 years!” This is a reference to a legend about Gen. John Pershing in the Philippines that historians say is not true. Trump previously referenced the story in a rally in February 2016.

“They were having terrorism problems, just like we do,” Trump said. “And he caught 50 terrorists who did tremendous damage and killed many people. And he took the 50 terrorists, and he took 50 men and he dipped 50 bullets in pigs’ blood — you heard that, right? He took 50 bullets, and he dipped them in pigs’ blood. And he had his men load his rifles, and he lined up the 50 people, and they shot 49 of those people. And the 50th person, he said: You go back to your people, and you tell them what happened. And for 25 years, there wasn’t a problem. Okay? Twenty-five years, there wasn’t a problem.”

He later referenced this story again in March 2016. However, at that telling he said there wasn’t a problem for 28 years.

The use of the pigs’ blood against Muslim terrorists would be due to the consumption of pork being forbidden in Islam.